The development of dynamic networks has led to a wide range of location detection possibilities for objects of interest (people, goods, etc.). Location information for an object may be determined using several techniques. For example, the location of an object may be determined and transmitted from the object itself using, for example, Global Positioning System technology (“GPS”), triangulation, cellular networks, etc. Additionally, location information for an object may be determined using sensors with known positions. For example, if an object comes within a range of a sensor with a known position, the location of the object may be determined to be within the range of the known location of the sensor.
One or more objects of interest may move freely within an area in which a wireless sensor network (“WSN”) has been deployed. Each object of interest may be associated with a signature, which may comprise a transmitting or non-transmitting (e.g., active or passive) identification component. Non-transmitting identification components may include, for example, a visual signature (e.g., identified with camera face recognition) a heat signature, a RFID tag, etc. Transmitting identification components may include a technological signal. The technological signal may comprise a signal emitted from a wireless communication device, for example, a WiFi, Bluetooth, or cellular network request.
The WSN may further include one or more sensors. The sensors in the WSN may be characterized as anchored or mobile, and/or connected to or unconnected to a network (e.g., a communications network). A sensor may be capable of collecting, storing, and transmitting electronic data. Additionally, a sensor may be capable of updating accurate location data for itself if a known location detection method is available. For example, some sensors may comprise a device with satellite navigation, such as GPS.
An anchored sensor may be defined as a sensor that remains in a fixed position within the network and has accurate, static location data for itself. In contrast, a mobile sensor may change position, and may or may not have accurate location data for itself. Thus, sensors may be fixed or moving freely within a WSN.
A connected sensor may be defined as a sensor that can reliably transmit data to and receive data from a data storage and/or computation device in the WSN. In some instances, a connected sensor may have a wireless connection to other nodes or devices in the network, and in others, a connected sensor may have a wired (e.g., Ethernet) connection to other nodes or devices in the network. An unconnected sensor may be defined as a sensor that cannot reliably transmit data to and receive data from another device in the network.
Past precedents for location detection in sensor networks may fall into a few common categories. For example, one location detection procedure may assume the basis of static location triangulation, such as from cell towers or satellites. Other location detection procedures may assume the motion of sensors and the constant re-triangulation from neighboring nodes. In 2009, Wei Xi and other researchers published an improved approach in which the speed of motion of a sensor is also taken into consideration in the location calculation: EUL: an Efficient and Universal Localization Method for Wireless Sensor Network (2009, Wei Xi et al). Such continuous calculation however is done (as in this example) by each node, and thus such location determining solutions require significant computational costs on a device attached to each object being tracked.